As is well known in the art, thin film magnetic heads used with data storage apparatus, such as disk files, typically comprise a magnetic yoke formed with two pole pieces designated as P1 and P2 and an electrically conductive coil structure disposed between the pole pieces. The tips of the pole pieces define a transducing gap for coaction with a magnetic medium, such as a magnetic disk that rotates close to the transducing gap of the head. The pole pieces interconnect at a back closure. A polished ceramic substrate having a thin insulation layer thereon, which is lapped and polished, supports the different layers which are deposited to form the magnetic transducer. To prevent electrical shorting, insulating layers are provided between the coil structure and pole pieces.
During operation in the recording mode of a data storage device, such as a disk drive, current representing data signals is directed to the conductive coils. The current is converted to magnetic flux signals by the magnetic head or transducer, and the signals are recorded on the disk as it rotates adjacent to the nonmagnetic transducing gap. During the readout or playback mode, as the magnetic disk is rotated past the head, the recorded magnetic flux signals are sensed and are converted to current that flows through the conductive coils. U.S. Pat. No. 4,694,368 which issued to Bischoff et al. on Sep. 15, 1987 describes a process of making a thin film magnetic head or transducer.
A significant problem that is experienced with thin film magnetic heads is the relatively high coil resistance or transducer resistance. The power I.sup.2 R (where I is current and R is resistance) that is dissipated during the recording process is determined by the value of coil resistance Thus the higher the resistance, of the head coil structure the higher will be the power dissipation and the greater the extent of thermal expansion of the components of the recording head and the recording apparatus. Thermal expansion adversely affects the recording operation. In addition, during the readout mode, the amount of thermal noise that is generated depends upon the level of coil resistance. This thermal noise is generated at the transducer level and will be amplified in the storage apparatus, resulting in an undesirable reduction of the signal-to-noise ratio of the recording process.
An important factor to be considered in the design of a recording head is the number of coil windings or turns which are used and the overall length of the coil structure. The number of coil turns and the total length of the coil structure determine the overall resistance of the coil structure and signal output. One parameter that is important in read-write coil design is the overall resistance of the coil. Coil resistance is a function of the average cross-sectional dimensions of the coil as well as the coil length. Lower resistance allows more write current to be carried without increasing the heat being generated in the coil. Since thin film transducers are manufactured in layers using various materials and deposition techniques, it is desirable that the depth of the coil layer that is disposed intermediate the layers that contain the leg members of the yoke, be kept short to avoid problems that arise in depositing thick layers of magnetic material.
In the prior art, the process of manufacturing a bi-level coil require depositing one coil and then depositing a second coil on the first coil so that each turn of the second coil is aligned exactly with the corresponding turns of the first coil. The alignment of the coils in the two layers becomes very critical and is difficult to monitor during the process to determine if the various tolerances involved with the masks and associated processing have combined to introduce problems that are not detectable until after the transducer is completed. The present invention is directed to a process of manufacturing a thin film magnetic transducer which avoids the above-described problems.